Test Driven Development with ChatGPT

Andrii Kucherenko

https://t.me/mathrandomcommunity

https://mathrandom.com

YouTube: @mathrandomjavascriptcommunity

https://codeberry.club/

TDD

Navigation map
Test first
Assert first
Fail first

Navigation Map

Decomposition of the task
Less technical details
Clear and ready to share with other teams members
Can be changed during development

Test First

// calculator.spec.ts

test('should summarize two numbers', 
    (t: ExecutionContext) => {

    }
);

Assert First

// calculator.spec.ts

test('should summarize two numbers', 
    (t: ExecutionContext) => {
        t.is(sum(1, 2), 3);
    }
);

Fail First

➜  ava-ts git:(master) ✗ npm test

> ava-ts@1.0.0 test /Users/andrii_kucherenko/Workspace/lab/tdd-training/ava-ts
> ava



  1 uncaught exception

  Uncaught exception in __tests__/caclulator.spec.ts

  __tests__/caclulator.spec.ts(4,8): error TS2304: Cannot find name 'sum'.

npm ERR! Test failed.  See above for more details.

Fail First

➜  ava-ts git:(master) ✗ npm test

> ava-ts@1.0.0 test /Users/andrii_kucherenko/Workspace/lab/tdd-training/ava-ts
> ava



  1 uncaught exception

  Uncaught exception in __tests__/caclulator.spec.ts

  __tests__/caclulator.spec.ts(5,20): error TS2345: Argument of type '3' is not assignable to parameter of type 'void'.

Fail First

➜  ava-ts git:(master) ✗ npm test

> ava-ts@1.0.0 test /Users/andrii_kucherenko/Workspace/lab/tdd-training/ava-ts
> ava



  1 test failed

  should summarize two numbers

  /Users/andrii_kucherenko/Workspace/lab/tdd-training/ava-ts/__tests__/caclulator.spec.ts:5

   4: test('should summarize two numbers', (t: ExecutionContext) => {
   5:   t.is(sum(1, 2,), 3);
   6: });

  Difference:

  - 0
  + 3

npm ERR! Test failed.  See above for more details.

Benefits

Bridge from task to implementation
Improved code
Tests as documentation
Safe refactoring
No extra code
Increases assurance of correctness

TDD can:

Improve performance of development
Reduce the costs
Help to change the project
Reduce technical debt

TDD Kata

String Calculator

This classic kata guides you step by step through the implementation of a calculator that receives a String as input.

It is a good exercise on refactoring and incremental implementation. It is also a good candidate for practising TDD.

String calculator

First step

Create a function add that takes a String and returns a Number.

The method can take 0, 1 or 2 numbers separated by comma, and returns their sum.
An empty string will return “0”.
Example of inputs: "", "1", "1.1,2.2".